1. Field of the Invention
The present invention generally relates to a resolver circuit utilizing a bridge tied load (BTL) amplifier.
2. Description of Related Art
Resolver circuits are well known for many automotive applications. One such application includes electric power assisted steering (EPAS). EPAS systems employ a brushless motor to provide variable steering assist. An inductive sine-cosine resolver is used to provide the motor position and motor speed to a system microprocessor. The resolver is a transformer with a stationary portion called the stator and a rotating core called a rotor. The contour of the rotor forms a specially curved air gap between the stator and the rotor. The varying of the air gap changes the permeance of the resolver as a sinusoidal wave corresponding to the position or angle of the rotor shaft. During rotation, an excitation signal is provided to an excitation winding in the stator causing the voltage of the output windings to change in proportion to the angle of the rotor shaft. A processing circuit then analyzes the voltage changes to determine the rotor position and speed.
Known resolver circuits are generally complex requiring many parts to provide the excitation signal with the specified amplitude and a high accuracy over a wide range of battery voltages. In view of the above, is apparent that there exists a need for an improved resolver circuit having reduced complexity while maintaining performance specifications.